- From: Michael Kifer <kifer@cs.sunysb.edu>
- Date: Wed, 22 Jun 2005 13:16:52 -0400
- To: Jim Hendler <hendler@cs.umd.edu>
- Cc: Jos de Bruijn <jos.debruijn@deri.org>, dreer@fh-furtwangen.de, public-sws-ig@w3.org
Jim Hendler wrote:
>
> Jos-
> that's not quite right as I understand it - to use an example from
> the paper I cited -
>
> Given an ontology containing only a single RDF triple:
> <#pat> <#knows> <#jo>.
> the answer to a query asking if pat knows exactly one person would be
> "no" under
> RDF's open world semantics, but "yes" under the closed world
> semantics of Datalog.
>
> there's no negation explicit here.
Jim,
This is an invalid example. "Exactly one" cannot be expressed in RDF or DLP.
You have to be precise as to which definition of language extension you are
using. According to the one that I gave in my previous message (which is
a standard definitions--there are possibly others), the above example
doesn't disprove that LP is not an extension of DLP.
It is possible to argue that LP doesn't extend RDF with a different
argument: RDF has all kinds of ill-conceived baggage, like blank nodes.
If you interpret them as head-existentials, then this is not in Datalog.
But nobody in LP thinks much about blank nodes anyway---people approximate them
via Skolem constants. (OWL-DL is not layered on top of RDFS -- anybody
looses sleep over it?)
regards
--michael
> btw, this is not a small issue to me -- without some way to control
> default reasoning (i.e. limit the scope of axioms and facts that are
> considered for a set of queries) there is just no way to link things
> reliably on the Web (and without the linking, why bother with Web).
> As far as I'm concerned, the minute one assumes there is a
> mechanism to close a graph (and several are floating around), then
> ontology and rules go together just fine and lots of the layering is
> fixed. On the other hand, if a rule can be stated in general that
> has a negation as failure then we have a problem.
> In the old days, for example my thesis work, we used "ThNOT" in
> langauges like MicroPlanner, NASL, etc. and that was some of the
> earliest work on this stuff. The idea was you could use a rule like
> this
> P :- ThNOT Q.
> to mean P is true if you cannot prove Q. Implicit in this, and many
> of the systems since, was the idea that there existed "A knowledge
> base" which was all the facts that this rule could be used on.
> On the Web, I would want this to read something like
> P :- (Thnot Q) given R.
> where "given R" somehow means with respect to some database, some
> graph, or some other nameable and definable entity.
> Thus, for example, one could imagine running a query against some
> graph (and note in theory that this could be the identity query,
> meaning it is equal to everything in the graph) and then stating that
> some set of rules is applied with respect to the resulting graph.
> These rules having NAF would be great and good and wonderful. If I
> applied your rules to a different graph, it would be up to me to
> decide if I wanted to restrict things in my graph to control the
> scope of the application of your rules -- this sounds like a powerful
> and crucial mechanism, and with it a lot could be done. Without it,
> rules on the web seem to me to either be just doing logic programming
> with a consistent syntax (in which case why invent all these
> languages, let's just use Prolog on the Web) or pretending the whole
> Web can be treated like a closed world - and that's, in my mind,
> where the dragons are...
> JH
>
>
>
> At 10:46 -0400 6/22/05, Jim Hendler wrote:
> >At 12:04 +0200 6/22/05, Jos de Bruijn wrote:
> >>-----BEGIN PGP SIGNED MESSAGE-----
> >>Hash: SHA1
> >>
> >>Dreer Michael WI wrote:
> >>
> >>>Hello,
> >>>
> >>>what is the relationship between WRL and SWRL?
> >>
> >>Hello Michael, others,
> >>
> >>With WRL we take an approach different from SWRL. We build on the
> >>experience in
> >>the Logic Programming and Deductive Database communities (and
> >>partially other rules communities) and (syntactically) restrict
> >>ourselves to Horn and add nonmonotonic negation, whereas SWRL stays
> >>within a First-order framework and simply extends the expressiveness
> >>of OWL DL. WRL extends a subset of OWL DL; this subset which falls in
> >>the framework of standard Horn rules.
> >>
> >>
> >
> >Sorry, but this cannot be right. SWRL assumes closed world
> >semantics and WRL assumes open world semantics. Thus, we get
> >completely different entailments in an OWL/RDF world than in a WRL
> >one, so we are talking something very different than a subset
> >relationship. Ian Horrocks, Peter Patel-Schneider, and Bijan Parsia
> >(with me as a kibbitzer) wrote a short paper about this available at
> >[1]
> >
> >Let me be clear, I'm all for Web (and Sem Web) rules languages, but
> >if it isn't open-world, I don't see how it can be Sem Web, since it
> >violates the base assumption on which all of RDF, RDFS, and OWL sit.
> >This is easily fixable, and at the Rules workshop the idea of a
> >"Scoped Negation as Failure" was developed to handle this -- I'd
> >love to see WRL (and SWRL) extended to have a SNAF mechanism,
> >because then we don't violate the basic principles of the Web
> >architecture and the Semantic Web, but we should be precise - two
> >things with very different Semantics and entailments cannot be
> >referred to as subsets of each other.
> >
> > -JH
> >
> >
> >
> >
> >[1] http://www.cs.man.ac.uk/~horrocks/Publications/download/2005/HPPH05.pdf
> >
> >>Best, Jos
> >>
> >>>
> >>>Thanks in advance
> >>>
> >>>Michael Dreer
> >>>
> >>>
> >>
> >>> Steve Ross-Talbot wrote:
> >>>
> >>> >>Out of curiosity and also business pragmatics what is the relationship
> >>> >>between WRL and RuleML?
> >>>
> >>>
> >>>
> >>> RuleML provides an extensive lattice of sublanguages ranging from
> >>> production rules to regular LP rules to First-Order Logic, es well as
> >>> sublanguages with such features as slotted syntax, meta-programming, and
> >>> courteous logic programming.
> >>>
> >>> WRL makes a choice to use include particular features in the language.
> >>> It turns out that these features correspond to certain RuleML
> >>> sublanguages to a great extent. Therefore, RuleML can be used for the
> >>> XML serialization of a large part of the language.
> >>>
> >>> The following document describes the (RuleML and other) schemas used for
> >>> the XML serialization of WRL:
> >>>
> >>> http://www.wsmo.org/wsml/wrl/wrl-xmlschemas.html
> >>>
> >>> More details on the XML serialization of WRL can be found at:
> >>>
> >>> http://www.wsmo.org/wsml/wrl/wrl.html#cha:wrl-xml
> >>>
> >>> I hope this clarifies the issue.
> >>>
> >>>
> >>> Best, Jos
> >>>
> >>>
> >>> >>Cheers
> >>> >>
> >>> >>Steve T
> >>> >>
> >>> >>On 21 Jun 2005, at 08:28, Jos de Bruijn wrote:
> >>> >>
> >>> >>Dear all,
> >>> >>
> >>> >>On behalf of WSML, AIFB and NRCC I am pleased to announce:
> >>> >>
> >>> >>The Web Rule Language WRL - version 1.0:
> >>> >>
> >>> >>http://www.wsmo.org/wsml/wrl/
> >>> >>
> >>> >>
> >>> >>WRL is a rule language for the Web and the Semantic Web and was
> >>> >>heavily influenced by the Web Service Modeling Language WSML
> >>> >>(http://www.wsmo.org/wsml/wsml-syntax).
> >>> >>
> >>> >>
> >>> >>Best regards,
> >>> >>
> >>> >>Jos de Bruijn
> >>> >>
> >>> >>>>
> >>> >>>>
> >>>
> >>>
> >>> --
> >>> Jos de Bruijn, http://www.uibk.ac.at/~c703239/
> >>> +43 512 507 6475 jos.debruijn@deri.org
> >>>
> >>> DERI http://www.deri.org/
> >>> ----------------------------------------------
> >>>
> >>> Only two things are infinite, the universe and
> >>> human stupidity, and I'm not sure about the
> >>> former.
> >>> -- Albert Einstein
> >>
> >>
> >>- --
> >>Jos de Bruijn, http://www.uibk.ac.at/~c703239/
> >>+43 512 507 6475 jos.debruijn@deri.org
> >>
> >>DERI http://www.deri.org/
> >>- ----------------------------------------------
> >>
> >>Only two things are infinite, the universe and
> >>human stupidity, and I'm not sure about the
> >>former.
> >> -- Albert Einstein
> >>-----BEGIN PGP SIGNATURE-----
> >>Version: GnuPG v1.2.5 (GNU/Linux)
> >>Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org
> >>
> >>iD8DBQFCuTeV4lqeiwiiHN4RAm8yAJ491RyZZhgDHODjtbIiwT/esmS3IgCfZ3Ws
> >>xyLcZkDOCDxFNHoHi/DLVeQ=
> >>=UHcZ
> >>-----END PGP SIGNATURE-----
> >
> >--
> >Professor James Hendler Director
> >Joint Institute for Knowledge Discovery 301-405-2696
> >UMIACS, Univ of Maryland 301-314-9734 (Fax)
> >College Park, MD 20742 http://www.cs.umd.edu/users/hendler
>
> --
> Professor James Hendler Director
> Joint Institute for Knowledge Discovery 301-405-2696
> UMIACS, Univ of Maryland 301-314-9734 (Fax)
> College Park, MD 20742 http://www.cs.umd.edu/users/hendler
> --============_-1092663174==_ma============
> Content-Type: text/html; charset="us-ascii"
>
> <!doctype html public "-//W3C//DTD W3 HTML//EN">
> <html><head><style type="text/css"><!--
> blockquote, dl, ul, ol, li { padding-top: 0 ; padding-bottom: 0 }
> --></style><title>Re: Web Rule Language - WRL vs
> SWRL</title></head><body>
> <div>Jos-</div>
> <div> that's not quite right as I understand it - to use an
> example from the paper I cited -</div>
> <div><br></div>
> <div>Given an ontology containing only a single RDF triple:</div>
> <div><#pat> <#knows> <#jo>.</div>
> <div>the answer to a query asking if pat knows exactly one person
> would be "no" under<br>
> RDF's open world semantics, but "yes" under the closed world
> semantics of Datalog.</div>
> <div><br></div>
> <div>there's no negation explicit here.</div>
> <div><br></div>
> <div> btw, this is not a small issue to me -- without some way to
> control default reasoning (i.e. limit the scope of axioms and facts
> that are considered for a set of queries) there is just no way to link
> things reliably on the Web (and without the linking, why bother with
> Web). </div>
> <div> As far as I'm concerned, the minute one assumes there is a
> mechanism to close a graph (and several are floating around), then
> ontology and rules go together just fine and lots of the layering is
> fixed. On the other hand, if a rule can be stated in general
> that has a negation as failure then we have a problem.</div>
> <div> In the old days, for example my thesis work, we used
> "ThNOT" in langauges like MicroPlanner, NASL, etc. and that
> was some of the earliest work on this stuff. The idea was you
> could use a rule like this</div>
> <div> P :- ThNOT Q.</div>
> <div>to mean P is true if you cannot prove Q. Implicit in this,
> and many of the systems since, was the idea that there existed "A
> knowledge base" which was all the facts that this rule could be
> used on. </div>
> <div>On the Web, I would want this to read something like</div>
> <div> P :- (Thnot Q) given R.</div>
> <div>where "given R" somehow means with respect to some
> database, some graph, or some other nameable and definable entity.
> </div>
> <div> Thus, for example, one could imagine running a query
> against some graph (and note in theory that this could be the identity
> query, meaning it is equal to everything in the graph) and then
> stating that some set of rules is applied with respect to the
> resulting graph. These rules having NAF would be great and good
> and wonderful. If I applied your rules to a different graph, it
> would be up to me to decide if I wanted to restrict things in my graph
> to control the scope of the application of your rules -- this sounds
> like a powerful and crucial mechanism, and with it a lot could be
> done. Without it, rules on the web seem to me to either be just
> doing logic programming with a consistent syntax (in which case why
> invent all these languages, let's just use Prolog on the Web) or
> pretending the whole Web can be treated like a closed world - and
> that's, in my mind, where the dragons are...</div>
> <div> JH</div>
> <div><br></div>
> <div> </div>
> <div><br></div>
> <div>At 10:46 -0400 6/22/05, Jim Hendler wrote:</div>
> <div>>At 12:04 +0200 6/22/05, Jos de Bruijn wrote:<br>
> >>-----BEGIN PGP SIGNED MESSAGE-----<br>
> >>Hash: SHA1<br>
> >><br>
> >>Dreer Michael WI wrote:<br>
> >><br>
> >>>Hello,<br>
> >>><br>
> >>>what is the relationship between WRL and SWRL?<br>
> >><br>
> >>Hello Michael, others,<br>
> >><br>
> >>With WRL we take an approach different from SWRL. We build on
> the<br>
> >>experience in<br>
> >>the Logic Programming and Deductive Database communities
> (and<br>
> >>partially other rules communities) and (syntactically)
> restrict<br>
> >>ourselves to Horn and add nonmonotonic negation, whereas SWRL
> stays<br>
> >>within a First-order framework and simply extends the
> expressiveness<br>
> >>of OWL DL. WRL extends a subset of OWL DL; this subset which
> falls in<br>
> >>the framework of standard Horn rules.<br>
> >><br>
> >><br>
> ><br>
> >Sorry, but this cannot be right. SWRL assumes closed world
> semantics and WRL assumes open world semantics. Thus, we
> get completely different entailments in an OWL/RDF world than in a WRL
> one, so we are talking something very different than a subset
> relationship. Ian Horrocks, Peter Patel-Schneider, and Bijan
> Parsia (with me as a kibbitzer) wrote a short paper about this
> available at [1]<br>
> ><br>
> >Let me be clear, I'm all for Web (and Sem Web) rules languages,
> but if it isn't open-world, I don't see how it can be Sem Web, since
> it violates the base assumption on which all of RDF, RDFS, and OWL
> sit. This is easily fixable, and at the Rules workshop the idea of a
> "Scoped Negation as Failure" was developed to handle this --
> I'd love to see WRL (and SWRL) extended to have a SNAF mechanism,
> because then we don't violate the basic principles of the Web
> architecture and the Semantic Web, but we should be precise - two
> things with very different Semantics and entailments cannot be
> referred to as subsets of each other.</div>
> <div>><br>
> > -JH<br>
> ><br>
> ><br>
> ><br>
> ><br>
> >[1]
> http://www.cs.man.ac.uk/~horrocks/Publications/download/2005/HPPH05.p<span
> ></span>df<br>
> ><br>
> >>Best, Jos<br>
> >><br>
> >>><br>
> >>>Thanks in advance<br>
> >>><br>
> >>>Michael Dreer<br>
> >>><br>
> >>><br>
> >><br>
> >>> Steve Ross-Talbot wrote:<br>
> >>><br>
> >>> >>Out of curiosity and also business
> pragmatics what is the relationship<br>
> >>> >>between WRL and RuleML?<br>
> >>><br>
> >>><br>
> >>><br>
> >>> RuleML provides an extensive lattice of
> sublanguages ranging from<br>
> >>> production rules to regular LP rules to First-Order
> Logic, es well as<br>
> >>> sublanguages with such features as slotted syntax,
> meta-programming, and<br>
> >>> courteous logic programming.<br>
> >>><br>
> >>> WRL makes a choice to use include particular
> features in the language.<br>
> >>> It turns out that these features correspond to
> certain RuleML<br>
> >>> sublanguages to a great extent. Therefore, RuleML
> can be used for the<br>
> >>> XML serialization of a large part of the
> language.<br>
> >>><br>
> >>> The following document describes the (RuleML and
> other) schemas used for<br>
> >>> the XML serialization of WRL:<br>
> >>><br>
> >>>
> http://www.wsmo.org/wsml/wrl/wrl-xmlschemas.html<br>
> >>><br>
> >>> More details on the XML serialization of WRL can be
> found at:<br>
> >>><br>
> >>>
> http://www.wsmo.org/wsml/wrl/wrl.html#cha:wrl-xml<br>
> >>><br>
> >>> I hope this clarifies the issue.<br>
> >>><br>
> >>><br>
> >>> Best, Jos<br>
> >>><br>
> >>><br>
> >>> >>Cheers<br>
> >>> >><br>
> >>> >>Steve T<br>
> >>> >><br>
> >>> >>On 21 Jun 2005, at 08:28, Jos de Bruijn
> wrote:<br>
> >>> >><br>
> >>> >>Dear all,<br>
> >>> >><br>
> >>> >>On behalf of WSML, AIFB and NRCC I am
> pleased to announce:<br>
> >>> >><br>
> >>> >>The Web Rule Language WRL - version
> 1.0:<br>
> >>> >><br>
> >>> >>http://www.wsmo.org/wsml/wrl/<br>
> >>> >><br>
> >>> >><br>
> >>> >>WRL is a rule language for the Web and the
> Semantic Web and was<br>
> >>> >>heavily influenced by the Web Service
> Modeling Language WSML<br>
> >>> >>(http://www.wsmo.org/wsml/wsml-syntax).<br>
> >>> >><br>
> >>> >><br>
> >>> >>Best regards,<br>
> >>> >><br>
> >>> >>Jos de Bruijn<br>
> >>> >><br>
> >>> >>>><br>
> >>> >>>><br>
> >>><br>
> >>><br>
> >>> --<br>
> >>> Jos de Bruijn, http://www.uibk.ac.at/~c703239/<br>
> >>> +43 512 507 6475 jos.debruijn@deri.org<br>
> >>><br>
> >>> DERI http://www.deri.org/<br>
> >>> ----------------------------------------------<br>
> >>><br>
> >>> Only two things are infinite, the universe and<br>
> >>> human stupidity, and I'm not sure about the<br>
> >>> former.<br>
> >>> -- Albert Einstein<br>
> >><br>
> >><br>
> >>- --<br>
> >>Jos de Bruijn, http://www.uibk.ac.at/~c703239/<br>
> >>+43 512 507 6475
> jos.debruijn@deri.org<br>
> >><br>
> >>DERI <span
> ></span
> >
> http://www.deri.org/<br>
> >>- ----------------------------------------------<br>
> >><br>
> >>Only two things are infinite, the universe and<br>
> >>human stupidity, and I'm not sure about the<br>
> >>former.<br>
> >> -- Albert Einstein<br>
> >>-----BEGIN PGP SIGNATURE-----<br>
> >>Version: GnuPG v1.2.5 (GNU/Linux)<br>
> >>Comment: Using GnuPG with Thunderbird -
> http://enigmail.mozdev.org<br>
> >><br>
> >>iD8DBQFCuTeV4lqeiwiiHN4RAm8yAJ491RyZZhgDHODjtbIiwT/esmS3IgCfZ<span
> ></span>3Ws<br>
> >>xyLcZkDOCDxFNHoHi/DLVeQ=<br>
> >>=UHcZ<br>
> >>-----END PGP SIGNATURE-----<br>
> ><br>
> >--<br>
> >Professor James Hendler<x-tab>
> </x-tab><x-tab>
> </x-tab><x-tab> </x-tab>
> Director<br>
> >Joint Institute for Knowledge
> Discovery<x-tab>
> </x-tab> <x-tab> </x-tab>
> 301-405-2696<br>
> >UMIACS, Univ of Maryland<x-tab>
> </x-tab><x-tab>
> </x-tab><x-tab> </x-tab>
> 301-314-9734 (Fax)<br>
> >College Park, MD 20742<x-tab>
> </x-tab><x-tab>
> </x-tab><x-tab> </x-tab>
> http://www.cs.umd.edu/users/hendler</div>
> <div><br></div>
> <x-sigsep><pre>--
> </pre></x-sigsep>
> <div>Professor James Hendler<x-tab>
> </x-tab><x-tab>
> </x-tab><x-tab> </x-tab>
> Director<br>
> Joint Institute for Knowledge
> Discovery<x-tab>
> </x-tab> <x-tab> </x-tab>
> 301-405-2696<br>
> UMIACS, Univ of Maryland<x-tab>
> </x-tab><x-tab>
> </x-tab><x-tab> </x-tab>
> 301-314-9734 (Fax)<br>
> College Park, MD 20742<x-tab>
> </x-tab><x-tab>
> </x-tab><x-tab> </x-tab>
> http://www.cs.umd.edu/users/hendler </div>
> </body>
> </html>
> --============_-1092663174==_ma============--
>
>
Received on Wednesday, 22 June 2005 17:17:07 UTC